Dense Si3N4 coatings with high friction coefficient deposited by high-velocity pulsed plasma spraying

A novel electromagnetically accelerated plasma spraying technique was applied to mixtures of aSi3N4, and alumina, yttria, and silica additives to deposit thin coatings (50-100 um) onto mirror-polished stainless steel surfaces. The dense coatings consisted of crystalline aSi3N4 with minor amounts of...

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Bibliographic Details
Published in:Journal of thermal spray technology 2006-09, Vol.15 (3), p.356-363
Main Authors: USUBA, S, HEIMANN, R. B
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
Metals. Metallurgy
Production techniques
Surface treatment
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Summary:A novel electromagnetically accelerated plasma spraying technique was applied to mixtures of aSi3N4, and alumina, yttria, and silica additives to deposit thin coatings (50-100 um) onto mirror-polished stainless steel surfaces. The dense coatings consisted of crystalline aSi3N4 with minor amounts of 11 SiAlON, traces of f3Si3N4 and Y3A15012 as well as a quinary Si-Al-N-O-Y glass. The adhesion strengths depended on the powder particle size showing values of > 77 MPa for coarse powders (median grain size 25 gm) and > 67 MPa for fine powders (median grain size 8 um). The average indentation hardnesses were 450 HV0.025 (coarse powder) and 620 HV0.025 (fine powder); the sliding wear resistances were comparable to those of sintered Si3N4 used as counterbody in a pin-on-disc friction test. The friction coefficient showed surprisingly large values (1.0-1.1 in water and 1.3-1.4 in air), suggesting application of such coatings as tribological high-friction surfaces.
ISSN:1059-9630
1544-1016
DOI:10.1361/105996306X124356